The basement membrane is fundamentally important: developmentally; in providing cellular orientation and structural organization of numerous tissues; and in tumor metastases. It is vital to understand the molecular composition, interactions and structure of the basement membrane constituents so that we may understand basement membrane function in health and disease. This proposal will focus on a major non-collageous glycoprotein called laminin, found in basement membrane. We will isolate and characterize laminin produced by a number of cells that seem to be of endodermal origin, (M15 and PYS) and one that may not be, (EHS). We will use immunoelectron-microscopy to study interaction of laminin, type IV collagen and fibronectin. It is important to study this under various conditions of culture in vitro to serve as a baseline in understanding peturbations of BM in disease and possibly how certain tumors may metastasize by the blood stream and others not. Functions of specific chains will be studied to ascertain whether there are segregated domains that subserve specific functions. It is important to determine what the functional and antigenic differences between the 200 and 400 KD fragments of laminin may be. This will be addressed using monoclonal antibodies and attempting to sort out these separate, or possibly overlapping functional or antigenic domains. These studies will provide a structural and biochemical baseline on the organization and interaction of some basement membrane components (laminin and type IV collagen), though not all. It is proposed that this will permit a more fundamental understanding of the basement membrane normally and its pathobiology in various disease states.